1. Technical Field
The present invention relates in general to reciprocating pumps and, in particular, to an improved system, method, and apparatus for a suction valve stop assembly in a reciprocating pump.
2. Description of the Related Art
In oil field operations, reciprocating pumps are often used for various purposes. Some reciprocating pumps, generally known as “service pumps,” are typically used for operations such as cementing, acidizing, or fracing a well. Typically, these service pumps run for relatively short periods of time, but they operate on a frequent basis. Often they are mounted to a truck or a skid for transport to various well sites. A pump might operate several times a week. In many applications, several pumps are connected in parallel to a single flow line.
As shown in FIG. 10, a reciprocating pump 101 typically has a plunger 103 for pumping a fluid through a cylinder 105. The cylinder has a fluid inlet 107 and a fluid outlet 109. An opening 111 in the pump 101 provides access to an interior of the cylinder 105. The opening 111 is sealed with a suction cover 115 and nut 116 that form a portion of a suction cover assembly 113. Suction cover assembly 113 also structurally supports a valve spring retainer 117. The valve spring retainer 117 seats in fluid inlet 107 and retains a spring 119 of the inlet valve 121. The valve spring retainer 117 also engages a hub 123. The hub 123 is eccentric or offset with respect to a central axis 125 of suction cover 115). Hub 123 protrudes from suction cover 115 to restrain valve spring retainer 117 during operation.
Importantly, suction cover 115 utilizes a set screw 122 that engages a threaded hole in cylinder 105, which thereby prevents rotation of suction cover 115 during operation. It is the eccentric positioning of the hub 123 that necessitates set screw 122 due to the torque applied by the valve spring retainer 117.
Suction cover assembly 113 can be disassembled and reassembled to provide access to and reseal the cylinder 105, respectively. However, the diametral clearance between suction cover 115 and valve spring retainer 117 (approximately 0.030″) is so tight that it is very difficult to realign and reseat these components with respect to the eccentric hub 123, which must be carefully repositioned to properly make-up with and support the valve spring retainer 117.
Since the clearance is tight, suction cover 115 not only guides valve spring retainer 117, but also supports the valve stop. Forces from fluid flow and spring 119 translate to the suction cover 115, and promote untimely failure of the suction cover 115 and cylinder 105. That tendency increases with time as cylinder 105 and valve spring retainer 117 engage and wear on each other due to the tight clearance. In addition, it is very difficult to align the eccentric hub 123 to valve spring retainer 117, and the set screw 122 to the hole in the cylinder 105 at the same time. Thus, an improved design for facilitating engagement between the various components of suction cover assemblies is needed.